1. Field of the Invention
The invention relates to a method of constructing a rail track and in particular to a method of constructing a rail track on a concrete slab in which the concrete slab is poured around anchor members for fixing tie plates supporting the rails of the rail track. The invention also relates to a temporary tie plate used in the method according to the invention.
2. Description of the Prior Art
Laying a rail track for metros or trams on a concrete slab by placing prefabricated rails directly onto tie plates at the location where the track is to be laid, the rails being suspended in their final position by means of a gantry with the tie plates fixed to the rails by attachments, is currently known in the art. A concrete slab is then poured under the rails, up to the height of the tie plates, which support anchor members consisting of threaded rods passing through the tie plates and having a bottom part embedded in the concrete slab. When the concrete has set, the tie plates are permanently immobilized on the concrete slab by tightening nuts onto the threaded rods, the nuts bearing on the top face of the tie plates.
In the above kind of construction method, it is necessary for the threaded rods to be held perfectly perpendicular to the tie plate when pouring the concrete to assure a good seating of the tie plate during subsequent tightening of the nuts onto the threaded rods. However, it is also necessary for the threaded rods not to be rigidly attached to the tie plate so that tightening the nuts, after the concrete has set, tensions the part of the threaded rods embedded in the concrete, for good retention of the threaded rods in the concrete slab.
Solving this problem by using elastic members or fusible members to hold the threaded rods on the tie plate during pouring of the concrete and which enable movement of the threaded rods relative to the tie plate when tightening the nuts is currently known in the art.
However, the above kind of elastic or fusible members have the drawback of not ensuring that the threaded rods are correctly perpendicular to the tie plates, which leads to imperfect seating of the tie plates during subsequent tightening of the nuts.
Also, one object of the present invention is to propose a method of building a rail track that enables accurate and perpendicular positioning of anchor members relative to the tie plate when pouring the concrete and uses anchor members that are independent of the tie plates when tightening the nuts after the concrete has set.